Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4
000
FXUS02 KWBC 020531
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
130 AM EDT MON MAY 02 2016

VALID 12Z THU MAY 05 2016 - 12Z MON MAY 09 2016

GENERAL FLOW PATTERN
~~~~~~~~~~~~~~~~~~~~
A PROGRESSIVE OMEGA BLOCK BREAKS DOWN SATURDAY INTO SUNDAY AS A
LARGE CLOSED LOW DEVELOPS ACROSS EASTERN CANADA, ENGULFING THE
EASTERN MEMBER/DEEP CYCLONE.  MEANWHILE, A SLOWLY PROGRESSIVE
RIDGE ACROSS THE EASTERN PACIFIC MOVES A CLOSED LOW OUT OF THE
WEST INTO THE HIGH PLAINS.  THE BIGGEST FLY IN THE OINTMENT LIES
ACROSS WESTERN CANADA AND OFFSHORE THE NORTHWEST, WHERE THE 18Z
GEFS/12Z NAEFS MEAN BECOME OUT OF PHASE WITH THE 12Z ECMWF AND ITS
ENSEMBLE MEAN.


MODEL PREFERENCES
~~~~~~~~~~~~~~~~~
FOR ANOTHER DAY, THE 18Z/00Z GFS BEST FIT THE ENSEMBLE MEAN
SOLUTIONS IN MOST PLACES.  THE ENSEMBLE MEAN GUIDANCE BECOMES OUT
OF PHASE NEAR 50N 140W AND ACROSS WESTERN CANADA FROM LATE
SATURDAY ONWARD.  AS THE ECMWF ENSEMBLE MEAN HAS ONLY RECENTLY
JOINED ITS OPERATIONAL RUN IN THIS AREA, BELIEVE THE BEST COURSE
FOR THE TIME BEING IS TO USE A COMPROMISE OF THE 18Z OR 00Z
GFS/12Z NAEFS MEAN/12Z ECMWF ENSEMBLE MEAN, WHICH SLOWLY
INTRODUCES THE POSSIBILITY INTO THE FORECAST.  THIS COMBINATION
WAS USED FOR MOST MEDIUM RANGE GRIDS.  THE DAYS 4-5 QPF WAS
COMPOSED OF A 18Z GFS/00Z GFS/12Z ECMWF COMPROMISE, WHILE THE DAYS
6-7 QPF WAS A CLOSER TO A 40/40/40 BLEND OF THE 18Z GFS/00Z
GFS/12Z ECMWF.


WEATHER HIGHLIGHTS/THREATS
~~~~~~~~~~~~~~~~~~~~~~~~~~
THE DEEP CYCLONE HEADING INTO THE WEST WILL SPREAD A BROAD AREA OF
RAIN AND HIGHEST ELEVATION SNOW FROM THE WEST COAST INTO THE
ROCKIES, WITH SOME RAINS DEVELOPING OVER THE PLAINS THIS WEEKEND
INTO NEXT MONDAY. THE HIGHEST TOTALS ARE EXPECTED ACROSS PORTIONS
OF CO AND WY AS WELL AS THE SIERRA NEVADA IN EASTERN CA.
TEMPERATURES ASSOCIATED WITH THE SYSTEM ARE EXPECTED TO BE 5-10F
BELOW THE MEAN FOR EARLY MAY.

RIDGING AHEAD OF THE CYCLONE IS EXPECTED TO LEAD TO 10-20F+
DEPARTURES FROM THE ROCKIES THURSDAY INTO THE PLAINS INTO THE
MIDWEST SATURDAY WITH 5-10F+ ANOMALIES FORECAST FOR THE EAST
MONDAY.

UPPER TROUGHING WITH ONE OR MORE EAST COAST/WESTERN ATLANTIC SFC
LOWS WILL GENERALLY SUPPORT COOL AND UNSETTLED WEATHER OVER THE
EAST FROM THURSDAY INTO SATURDAY.  MUCH OF THE PRECIPITATION IS
EXPECTED TO FALL ACROSS THE MID-ATLANTIC STATES THURSDAY INTO
SATURDAY AS WELL.  TEMPERATURES DURING THIS INTERVAL ARE EXPECTED
TO BE 4-8F BELOW THE AVERAGE FOR EARLY MAY.

ROTH
$$




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.